Man's attempts to imitate down with petroleum derived products have resulted in insulation that is cheaper than down, does not lose warmth (much) when wet, and is easy to dry out. It is however heavier and bulkier than down for the warmth given, and does not last as long. Thus although down remains a top choice for insulated clothes due to its light weight and low bulk relative to the warmth achieved, synthetic insulation is better in situations where clothing is likely to get damp, either from weather or from sweat. At present, its use is mainly confined to "Belay Jackets" (ie jackets that can be quickly pulled on over everything else while stationary on a belay) and as a lighter weight substitute for an extra warm mid layer fleece.
Synthetic Jackets & Pullovers : Jackets designed to provide extra warmth on stances and/or an extra warm mid-layer. Can also be used as general warm jackets for wandering around town in.
Synthetic Vests: Body-warming waistcoats. Very good at proving core warmth for minimal weight and very useful for ice-climbing as they can simply passed for climber to climber depending on who is belaying.
Synthetic Trousers: Synthetic fill overtrousers - great for high altitude base camps.